Thermoplastic molding compositions

ABSTRACT

A thermoplastic molding composition having improved mold release properties is provided, the composition comprising a thermoplastic resin selected from the group consisting of a high molecular weight linear polyester and a high molecular weight block copolyester, from about 0.1 to 4.5% by weight, based on the total composition, of a polyolefin or olefin-based copolymer, and, optionally, from about 0.02 to 0.5% by weight, based on the total composition, of talc.

BACKGROUND OF THE INVENTION

This invention relates to improved thermoplastic molding compositionsand, more particularly, to improved thermoplastic polyester andcopolyester molding compositions.

High molecular weight linear polyesters and copolyesters of glycols andterephthalic or isophthalic acid have been available for a number ofyears. These are described inter alia in Whinfield et al, U.S. Pat. No.2,465,319, and in Pengilly, U.S. Pat. No. 3,047,539, incorporated hereinby reference. These patents disclose that the polyesters areparticularly advantageous as film and fiber formers.

With the development of molecular weight control, the use of nucleatingagents and two-step molding cycles, poly(ethylene terephthalate) hasbecome an important constituent of injection-moldable compositions.Poly(1,4-butylene terephthalate), because of its very rapidcrystallization from the melt, is uniquely useful as a component in suchcompositions. Workpieces molded from such polyester resins, incomparison with other thermoplastics, offer a high degree of surfacehardness and abrasion resistance, high gloss, and lower surfacefriction.

Recently, block copolyesters, wherein the major portion of the repeatingunits are poly(1,4-butylene terephthalate) blocks, have been found tohave enhanced impact resistance.

It has now been discovered that if a small amount of a polyolefin orolefin-based copolymer is incorporated in the thermoplastic moldingcompositions, such as those described hereinbefore, the compositionsexhibit vastly improved mold releasability.

DETAILED DESCRIPTION OF THE INVENTION

According to this invention then, there are provided thermoplasticcompositions which are useful for molding or extrusion, e.g., injectionmolding, injection blow molding, compression molding, transfer molding,profile extrusion, sheet extrusion, wire coating, extrusion blow moldingand the like, the compositions have improved mold release and other goodphysical properties after molding, such as good surface appearance,comprising

(a) a thermoplastic resin selected from the group consisting of a linearhigh molecular weight polyester and a block copolyester derived from

(i) a terminally-reactive poly(1,4-butylene terephthalate) and

(ii) a terminally-reactive aromatic/aliphatic copolyester of adicarboxylic acid selected from the group consisting of terephthalicacid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indanedicarboxylic acid and compounds of the formula: ##STR1## in which X maybe alkylene or alkylidene of from 1 to 4 carbon atoms, carbonyl,sulfonyl, oxygen or a bond between the benzene rings, and an aliphaticdicarboxylic acid having from 6 to 12 carbon atoms in the chain and oneor more straight or branched chain dihydric aliphatic glycols havingfrom 4 to 10 carbon atoms in the chain, said copolyester having at least10% of aliphatic units being derived from a dicarboxylic acid, or

(iii) a terminally-reactive aliphatic polyester of a straight chainaliphatic dicarboxylic acid having from 4 to 12 carbon atoms in thechain and a straight or branched chain aliphatic glycol, said blocksbeing connected by inter terminal linkages consisting essentially ofester linkages;

(b) from about 0.1 to 4.5% by weight, based on the total composition, ofa polyolefin or olefin-based copolymer; and

(c) optionally, from about 0.02 to 0.5% by weight, based on the totalcomposition, of talc.

The high molecular weight linear polyesters used in the practice of thepresent invention are polymeric glycol esters of terephthalic acid andisophthalic acids. They are available commercially or can be prepared byknown techniques, such as by the alcoholysis of esters of the phthalicacid with a glycol and subsequent polymerization, by heating glycolswith the free acids or with halide derivatives thereof, and similarprocesses. These are described in U.S. Pat. No. 2,465,319 and U.S. Pat.No. 3,047,539, and elsewhere.

Although the glycol portion of the polyester can contain from two to tencarbon atoms, it is preferred that it contain from two to four carbonatoms in the form of linear methylene chains.

Preferred polyesters will be of the family consisting of high molecularweight, polymeric glycol terephthalates or isophthalates havingrepeating units of the general formula: ##STR2## wherein n is a wholenumber of from two to four, and mixtures of such esters, includingcopolyesters of terephthalic and isophthalic acids of up to about 30mole percent isophthalic units.

Especially preferred polyesters are poly(ethylene terephthalate) andpoly(1,4-butylene terephthalate). Special mention is made of the latterbecause it crystallizes at such a good rate that it may be used forinjection molding without the need for nucleating agents or long cycles,as is sometimes necessary with poly(ethylene terephthalate).

Illustratively, high molecular weight polyesters will have an intrinsicviscosity of at least about 0.4 deciliters/gram and, preferably, atleast 0.7 deciliters/gram as measured in a 60:40phenol-tetrachloroethane mixture at 30° C. At intrinsic viscosities ofat least about 1.1 deciliters/gram, there is a further enhancement intoughness of the present compositions.

The block copolyesters useful in the composition of this invention areprepared by the reaction of terminally-reactive poly(butyleneterephthalate), preferably, low molecular weight, and aterminally-reactive copolyester or polyester in the presence of acatalyst for transeterification, such as zinc acetate, manganeseacetate, titanium esters, and the like. The terminal groups can comprisehydroxyl, carboxyl, carboalkoxy, and the like, including reactivederivatives thereof. The result of reaction between two terminallyreactive groups, of course, must be an ester linkage. After initialmixing, polymerization is carried out under standard conditions, e.g.,220 to 280° C., in a high vacuum, e.g., 0.1 to 2 mm Hg, to form theblock copolymer of minimum randomization in terms of distribution ofchain segments. These copolyesters are described in copending U.S.application Ser. No. 752,325, filed on Dec. 20, 1976, incorporatedherein by reference.

The copolyester designated component (ii), hereinabove, is preferablyprepared from terephthalic acid or isophthalic acid or a reactivederivative thereof and a glycol, which may be a straight or branchedchain aliphatic glycol. Illustratively, the glycol will be1,4-butanediol; 1,5-pentanediol; 1,6-hexanediol; 1,9-nonanediol;1,10-decanediol; neopentyl glycol; 1,4-cyclohexanediol; 1,4-cyclohexanedimethanol, a mixture of any of the foregoing, or the like. Illustrativeof suitable aliphatic dicarboxylic acids for the mixedaromatic/aliphatic embodiments are suberic, sebacic, azelaic, adipicacids and the like.

The copolyesters may be prepared by ester interchange in accordance withstandard procedures. The copolyesters designated (ii) are mostpreferably derived from an aliphatic glycol and a mixture of aromaticand aliphatic dibasic acids in which the mole ratio concentration ofaromatic to aliphatic acids is from between 1 to 9 to 1, with anespecially preferred range being from about 3 to 7 to about 7 to 3.

The terminally reactive aliphatic polyesters designated component (iii)will contain substantially stoichiometric amounts of the aliphatic dioland the aliphatic dicarboxylic acid, although hydroxy-containingterminal groups are preferred.

In addition to their ease of formation by well-known procedures, boththe aromatic/aliphatic copolyesters (ii) and the aliphatic polyesters(iii) are commercially available. One source for such materials is theRuco Division/Hooker Chemical Company, Hicksville, N.Y., whichdesignates its compounds as "Rucoflex."

The block copolyesters used in the invention preferably comprise from 95to 50 parts by weight of the segments of poly(1,4-butyleneterephthalate). The poly(1,4-butylene terephthalate) blocks, beforeincorporation into the block copolyesters, will preferably have anintrinsic viscosity of above 0.1 dl./g. and preferably, between 0.1 and0.5 dl./g., as measured in a 60:40 mixture of phenol/tetrachloroethaneat 30° C. The balance, 5 to 50 parts by weight of the copolyester willcomprise blocks of components (ii) or (iii).

As will be understood by those skilled in the art, the poly(1,4-butyleneterephthalate) block can be straight chain or branched, e.g., by use ofa branching component, e.g., 0.05 to 1 mole %, based on terephthalateunits, of a branching component which contains at least threeester-forming groups. This can be a glycol, e.g., pentaerythritol,trimethylolpropane, and the like, or a polybasic acid compound, e.g.,trimethyl trimestate, and the like.

The polyolefin or olefin-based copolymer additives of the presentinvention are, preferably, selected from polyethylene, including highand low density polyethylene, propylene-ethylene copolymer,ethylene-vinyl acetate copolymer, ethylene-acrylic acid copolymer, andthe like. Polyethylene is most preferred. These polymers are well knownto those skilled in the art and for the most part are commerciallyavailable. In general, the polyolefin or olefin-based copolymer additiveis employed in amounts ranging from about 0.1% by weight to 4.5% byweight of the total weight of the composition. Preferably, from about0.5 to about 2% by weight, of the total composition, is employed. Byvirtue of the presence of the polyolefin or olefin-based copolymeradditive, the compositions of the present invention exhibit significantimprovement in mold releasability.

Small amounts, such as from about 0.02 to about 0.5% by weight, based onthe total composition, of talc may be included in the composition ofthis invention. Compositions of polyester, polyolefin and talc exhibitgood mold releasability and good surface appearance.

The compositions of the present invention are prepared in conventionalways. For example, in one way, the polyolefin or olefin-based copolymer,and talc, if used, are all put into an extrusion compounder with thethermoplastic resin to produce molding pellets. The polyolefin orolefin-based copolymer, and talc, are dispersed in a matrix of thethermoplastic in the process. In another procedure, the polyolefin orolefin-based copolymer, are mixed with the thermoplastic resin by dryblending, then either fluxed on a mill and comminuted, or they areextruded and chopped. The polyolefin or olefin-based copolymer and talc,if used, can also be mixed with the powdered or granular thermoplasticresin and directly molded, e.g., by injection or transfer moldingtechniques. It is always important to thoroughly free the thermoplasticresin from as much water as possible.

In addition, compounding should be carried out to ensure that theresidence time in the machine is short; the temperature is carefullycontrolled, the friction heat is utilized, and an intimate blend betweenthe polyolefin or olefin-based copolymer and the thermoplastic resin isobtained.

Although it is not essential, best results are obtained if theingredients are pre-compounded, pelletized, and then molded.Pre-compounding can be carried out in conventional equipment. Forexample, after carefully pre-drying the thermoplastic resin, e.g., at125° C. for 4 hours, a single screw extruder is fed with a dry blend ofthe polyester and the polyolefin or olefin-based copolymer, the screwemployed having a long transition and metering section to ensuremelting. On the other hand, a twin screw extrusion machine, e.g., a 28mm Werner Pfleiderer machine can be fed with resin and additives at thefeed port. In either case, a generally suitable machine temperature willbe about 450° to 570° F.

The pre-compounded composition can be extruded and cut up into moldingcompounds such as conventional granules, etc., by standard techniques.

The compositions of this invention can be molded in any equipmentconventionally used for thermoplastic compositions. For example, withpoly(1,4-butylene-terephthalate), good results will be obtained in aninjection molding machine, e.g., of the Newbury type with conventionalcylinder temperature, e.g., 450° F. and conventional mold temperatures,e.g., 150° F. On the other hand, with poly(ethylene terephthalate),because of the lack of uniformity of crystallinization from interior toexterior of thick pieces, somewhat less conventional but stillwell-known techniques can be used. For example, a nucleating agent suchas graphite or a metal oxide, e.g., ZnO or MgO can be included andstandard mold temperature of at least 230° F. will be used.

In order that those skilled in the art may better understand how topractice the present invention, the following examples are given by wayof illustration and not by way of limitation.

EXAMPLES 1-6

The following formulations are mechanically blended, then extended andmolded into test pieces in a Van Dorn injection molding machine.

                  Table 1                                                         ______________________________________                                        Example     1     2      3     4    5    6    7                               ______________________________________                                        Ingredients                                                                   (parts by                                                                     weight)                                                                       VALOX 310.sup.a                                                                           98.5  98.3   98.9  98.7 99   97.5 97.5                            Microthene.sup.b                                                                          1.5   1.5    1.0   1.0                                            FN 510                                                                        Dow 435.sup.c                       1.0  2.5                                  Irganox           0.15         0.15                                           1093.sup.d                                                                    Ferro 904.sup.e   0.05         0.05                                           Talc                     0.1   0.1                                            Alathon 3892.sup.f                            2.5                             ______________________________________                                          Each of the above formulations exhibits improved mold releasability          compared to 100% poly (1,4butylene terephthalate) and has the following       physical properties                                                      

    Properties  --                                                                Notched Izod                                                                  inpact strength                                                               ft. lbs./in.                                                                              --    --     1.0   --   1.05 1.05                                 Unnotched Izod                                                                impact strength                                                               ft. lbs./in.                                                                              --    48.8   --    --   --   --   --                              Tensile strength                                                                          --    7540   7500  7400 7500 7400 7150                            psi                                                                           Elongation %                                                                              --     353    301   269  252  254  257                            Flex strength, psi                                                                        --            13,000                                                                             --   --   --   --                              Flex modulus, psi        334,000                                                                             --   --   --   --                              ______________________________________                                         .sup.a poly(1,4butylene terephthalate), about 0.9 intrinsic viscosity         measured in a solution of phenol and tetrachloroethane (60 : 40) at           30° C.) available from G.E.                                            .sup.b polyethylene having average particle size of less than 20 microns      sold by U.S.I. Chemicals, N.Y., N.Y.                                          .sup.c ethyleneacrylic acid copolymer, 3.5% acrylic acid (Dow Chemical        U.S.A.)                                                                       .sup.d tetrakis (3,5di-t-butyl-4-hydroxy phenyl propionyl oxy methyl)         methane                                                                       .sup.e diphenyl decylphosphite                                                .sup.f copolymer of ethylene and vinyl acetate, 25% vinyl acetate (U.S.I.     Chemicals)                                                               

EXAMPLES 7-9

The following formulations are mechanically blended, then extended andmolded into test pieces in a Van Dorn injection molding machine.

                  Table 2                                                         ______________________________________                                        Example   7            8        9                                             ______________________________________                                        Ingredients                                                                   (parts by                                                                     weight)                                                                       VALOX 330.sup.g                                                                         98.8         99.0     98.9                                          Microthene                                                                    FN 510    1.0          1.0      1.0                                           Ferro 904 0.05                                                                Irganox 1093                                                                            0.15                                                                talc                            0.1                                           ______________________________________                                         Each of the above formulations ehibits improved mold releasability            compared to 100% block copolyester and has the following physical             properties                                                               

    Example                                                                       ______________________________________                                        Properties                                                                    Notched Izod                                                                  impact strength                                                               ft. lbs./in. notch                                                                      1.71         1.94     1.35                                          unnotched Izod                                                                impact strength                                                               ft. lbs./in.                                                                            36.8         36.3                                                   tensile strength,                                                             psi       4960         4864     5200                                          elongation %                                                                            292.9        328.9    412                                           ______________________________________                                         .sup.g block copolyester of poly(1,4butylene terephthalate and poly           (1,6hexylene-(0.7) azelate(0.3) isophthalate)                            

The following formulations are mechanically blended, then extended andmolded into test pieces in a Van Dorn injection molding machine.

                  Table 3                                                         ______________________________________                                        Example      10          11      12                                           ______________________________________                                        Ingredients                                                                   (parts by                                                                     weight)                                                                       VALOX 315.sup.h                                                                            98.9        98.9    98.9                                         Microthene                                                                    FN 510       1                                                                talc         0.1         0.1     0.1                                          Epolene N-10.sup.i       1.0                                                  Dow 459.sup.j                    1.0                                          ______________________________________                                         Each of the above formulations exhibits improved mold releasability           compared to 100% poly (1,4butylene terephthalate) and Example 10 exhibits     exceptionally good surface appearance. The following additional physical      properties are also exhibited:                                           

    Example      10          11      12                                           ______________________________________                                        Properties                                                                    Notched Izod                                                                  impact strength                                                               ft. lbs./in. 1.05        0.9     1.1                                          Flex strength,                                                                             13,200      13,100  13,000                                       psi                                                                           Flex modulus,                                                                              350,000     361,000 354,000                                      psi                                                                           Tensile strength,                                                                          7,300       7,600   7,550                                        psi                                                                           elongation % 285         294     303                                          ______________________________________                                         .sup.h poly (1,4butylene terephthalate) intrinsic viscosity 1.1 in., a        solution of phenol and tetrachloroethane (60:40) at 30° C.             .sup.i low molecular weight polyethylene resin                                .sup.j ethyleneacrylic acid copolymer, 8% acrylic acid                   

Obviously, other modifications and variations of the present inventionare possible in light of the above teachings. It is, therefore, to beunderstood that changes may be made in the particular embodiments of theinvention described which are within the full intended scope of theinvention as defined by the appended claims.

I claim:
 1. An improved molding composition, having improved moldreleasability, said composition comprising:(a) a block copolymer derivedfrom blocks of(i) a terminally reactive poly(1,4-butylene terephthalate)and (ii) a terminally reactive aromatic/aliphatic copolyester of adicarboxylic acid selected from the group consisting of terephthalicacid, isophthalic acid, naphthalene dicarboxylic acids, phenyl indanedicarboxylic acid and compounds of the formula ##STR3## in which X maybe alkylene or alkylidene of from 1 to 4 carbon atoms, carbonyl,sulfonyl, oxygen or a bond between the benzene rings, and an aliphaticdicarboxylic acid having from 6 to 12 carbon atoms in the chain and oneor more straight or branched chain dihydric aliphatic glycols havingfrom 4 to 10 carbon atoms in the chain, said copolyester having at least10% of aliphatic units being derived from a dicarboxylic acid; or (iii)a terminally-reactive aliphatic polyester of a straight chain aliphaticdicarboxylic acid having from 4 to 12 carbon atoms in the chain and astraight or branched chain aliphatic glycol, said blocks being connectedby interterminal linkages consisting essentially of ester linkages; (b)from about 0.25 to 4.5 percent by weight, based on the totalcomposition, of a composition, of a polyolefin or olefin-basedcopolymer; and (c) from about 0.02 to about 0.5% by weight, based on thetotal composition, of talc.
 2. A composition as defined in claim 1wherein said polyolefin or olefin-based copolymer is selected from thegroup consisting of polyethylene, ethylene-acrylic acid copolymer andethylene-vinyl acetate copolymer.
 3. A composition as defined in claim 1wherein said polyolefin is polyethylene.
 4. A composition as defined inclaim 1 wherein said thermoplastic resin is a block copolyester derivedfrom blocks of(i) a terminally-reactive poly(1,4-butylene terephthalate)and (ii) a copolyester of isophthalic acid and a straight chainaliphatic dicarboxylic acid having from 6 to 12 carbon atoms in thechain with one or more straight or branched chain dihydric aliphaticglycols having from 4 to 10 carbon atoms in the chain.
 5. A compositionas defined in claim 4, wherein said block copolyester is derived fromblocks of(i) a terminally-reactive poly(1,4-butylene terephthalate) and(ii) a polyester of a straight chain aliphatic dicarboxylic acid havingfrom 6 to 12 carbon atoms and a branched chain dihydric aliphaticglycol.
 6. A composition as defined in claim 4 wherein said blockcopolyester is derived from blocks of(i) terminally-reactive poly(1,4-butylene terephthalate) and (ii)poly(1,6-hexylene-azelate-co-isophthalate).
 7. A composition as definedin claim 4 wherein said block copolyester is derived from blocks of(i)terminally-reactive poly(1,4-butylene terephthalate) and (ii)poly(1,6-hexylene-(0.7)-azelate-co-(0.3) isophthalate.
 8. A compositionas defined in claim 4 wherein said block copolyester is derived fromblocks of(i) terminally-reactive poly(1,4-butylene terephthalate) and(ii) poly(1,6-hexylene-adipate-co-isophthalate).
 9. A composition asdefined in claim 4 wherein said block copolyester is derived from blocksof(i) terminally-reactive poly(1,4-butylene terephthalate) and (ii)poly(1,6-hexylene-(0.5)-adipate-co-(0.5) isophthalate).
 10. Acomposition as defined in claim 4 wherein said block copolyester isderived from blocks of(i) terminally-reactive poly(1,4-butyleneterephthalate) and (ii)poly(1,6-hexylene-(0.7)-adipate-co-(0.3)-isophthalate).
 11. Acomposition as defined in claim 4 wherein said block copolyester isderived from blocks of(i) terminally-reactive poly(1,4-butyleneterephthalate) and (ii)poly(1,6-hexylene-co-neopentyl-adipate-co-isophthalate).
 12. Acomposition as defined in claim 4 wherein said block copolyester isderived from blocks of(i) terminally-reactive poly(1,4-butyleneterephthalate) and (ii) poly(neopentyl-adipate).
 13. A composition asdefined in claim 4 wherein said block copolymer is derived from blocksof(i) terminally-reactive poly(1,4-butylene terephthalate) and (ii)poly(1,4-butylene-adipate).
 14. A composition as defined in claim 4wherein said block copolyester is derived from blocks of(i)terminally-reactive poly(1,4-butylene terephthalate) and (ii)poly(ethylene-co-1,4-butylene-adipate).
 15. An improved flame-retardantthermoplastic molding composition, said composition comprising:(a) ablock copolyester derived from blocks of(i) terminally-reactivepoly(1,4-butylene terephthalate) and (ii)poly(1,6-hexylene-azelate-co-isophthalate); and (b) from about 0.1 to4.5 percent by weight, based on the total composition, of a polyolefinor olefin-based copolymer.
 16. A composition as defined in claim 15wherein said polyolefin or olefin-based copolymer is selected from thegroup consisting of polyethylene, ethylene-acrylic acid copolymer, andethylene-vinyl acetate copolymer.
 17. A composition as defined in claim15 wherein said polyolefin is polyethylene.
 18. A composition as definedin claim 15 wherein said polyolefin is low density polyethylene and saidpoly(1,6-hexylene-azelate-co-isophthalate ispoly(1,6-hexylene-(0.7)-azelate-co-(0.3) isophthalate.